Kneading in a twin screw processor, such as an extruder, involves application of forces that cause shearing, smearing, elongation, bending, torsion and compression. Progress of a material through the twin screw processor is generally highly controlled and such a system can be used to conduct sophisticated chemical reactions. For e.g., thermoplastic compounding requires standard conveying, mixing or kneading elements. The kneading elements mix compounds primarily through folding mechanism. This melting and folding mechanism results in fatigue in the elements which often causes breakage of the elements or the shaft.
U.S. Pat. No. 6,783,270 to Babu Padmanabhan, discloses fractional lobe elements. U.S. Publication number 2014/0036614 A1 to Babu Padmanabhan provides for extruder elements for co-rotating extruders that eliminate or reduce the peak shear experienced by material, increase distributive mixing for more homogeneous mixing and better melt temperature control and also maintain the self-wiping ability of the extruder. These elements comprise of a continuous flight where the flight transforms from an integer lobe flight into a non-integer lobe flight and transforms back to an integer lobe flight in a fraction of the lead ‘L’ or vice versa. Integer lobes or fractional lobes can be used to generate conveying screws (by continuous helical transformation) or kneading blocks (by interrupted linear and rotary transformations). Elements that are integer lobed or fractional lobed when designed as kneading blocks present a perpendicular face to the flow causing melt stagnation and large pressure and shear peaks during melting. Thus, these kneading block elements are not ideal for melting zone in an extruder as these elements are not capable of providing the required superior process capability in melting zone. Such elements also suffer from fatigue that may result in breakage.